Apparatus for measuring wire and the like



J ly 1952 R. J. COLE ET AL APPARATUS FOR MEASURING WIRE AND THE LIKE 2 SHEETS-SHEET 1 Filed Nov. 6. l94'7 INVENTORS ROBERT J." COLE BY EDWARD M. YARD ,7: ATTORfiEfi? July 15, 1952 R. J. COLE ETAL APPARATUS FOR MEASURING WIRE AND THE LIKE Filed Nov. 6. 1947 2 SHEETS-SHEET 2 INVENTORS ROBERT J. COLE av EDWARD M. Yum

xr- ATTORNE Patented July 15, 1952 APPARATUS FOR MEASURING AND THE LIKE Robert J. Cole, Yardley, Pa.,,and;Edward Yard, Trenton, N. .L, assignors to John A. Roeblings Sons Company, Trent0n, .N. .I., a corporation of New J ersey Application November 6, 1947,.Serial'No. 784,392

' 1 Claim. .(01. 175-1183) l his invention relates to apparatus and .a method for measuring the length. of elongated material-as it advances, .and is particularly applicable for measuring, at a given station, the

length -of ferromagnetic wire and the like-advanc'ing continuously athigh speed past said station. in additionto itsuse to measure length, the invention may be used to measure .or to control the speed of the advancing material.

In-the manufacture of wire, particularly during certain reeling operations, it is frequently desired to measure, as the wire advances, the length of wire wound up on a spool, with considerable eccuracy. A typical .speed of reeling ma i g or example; 1000 teet per minute. At such speeds, ,mechanical apparatus ior .measuring the length of the wire is subject to various diificulties. For example, such apparatus .may apply ,undue' tension to the wire.

A primary object of the present invention is to provide electromagnetic means and a method fer measuring the length of wire and the like while it advances .at a rapid rate. :It W ll Joe understood tha e i enti n may :be used or mea rin no o ly single w r s ,of different shapes. in. crossrsection. but also wire strand, rope, ribbonhcable, and the like, of ferromagnetic material.

A :feature of one embodiment of the present invention is that .itzis capable of'measuring the wire without: touching the wire, andshence without impeding the advancing motion of the wire.

Another object of the present invention is to provide, in combination with electromagnetic means for measuring wire as it is'beingreeled, means f or stopping "the reeling operation when a predetermined length of I wire has been; reeled.

Another feature of the present invention is that it is capable of -measuring accurately the length of ferromagnetic filamentary material, regardless'of the size or shape of thecrcss section of'thematerial.

Another object of the present invention is to provide apparatus and a. method for measuring the velocity of advancing ferromagnetic niamentary' material.

vAnother objector the presentinvention; is to provide a speed-controlling apparatus and methodfor use in'reeling wire and the like.

The'abo vementioned, as well as other 91 ,ie ts. t geth w th .th :man adva ta es obtainable by the practice of the present ,inven- =tion, w ill, be readilyzpemprehended :by persons skilled the art by reference to :the following 2 detailed descriptiontaken in connection with .the annexed drawings which respectively descrihe and illustrate a preferred .embocliment'of the invention, and wherein 1 is aschematic blockdiagrampf lengthmeasuring apparatus embodying the features of the .present invention.

Fig. 2 is a simplified circuit diagram ,of a length-measuring apparatus.

Fig. Bis a-circuit diagram ofa somewhat more complex -len gth-measuring apparatus.

Fig. 4 .is a semi-schematic diagram of apparatus capable of performing the functions .of measuring the length of wire as it; advances during a reeling operation, measuringthe velocity of the wire, controlling the speed 9f reeling .80 that the linear velocity of the wire is constant, n np the ree s t Qn when arredetermined length of wire has been reeled.

In o mbod n of h p e nt inven ionfq measuring the length of ferromagnetic wire while said wire is being advanced along a path thereis p vid d an e e t ma ti ,,-r r e head'posifi m e fi s stafion n s d :pa h or [ma zi p r o s of said w re such a short. spaced, el men a lensths Qf.-.s, me- .nn-electros e .pi -nnheadz s pos tioned a a .subse quent station on-said path, displaced from ,-,the recorder head lay a predetermined, known :disa c he-p upihead isad ptedtoigenerate electrical signals, such ,as pulses, in response .to passage of magnetizedportionsof the wire past the second station. :Qonnected @to the .pickrup head and responsive :to .the electrical signals from same are electrical circuit .means which are; also connected to the-recorder head, ,for'eners zi s sam These electrical circuit means may comprise a repeater such ,as .a controlled pulse generator, triggered or controlled by pulses from the pick-up head. A. counter,respon'siveto electrical signals- ,from the repeater, is provided 'forindicating Q he :length of :wire passing the device.

fIhe rQDerationof. such adevice may be asfollows. initiatori-mayfirstzbe operated :tocau'se the recorder head to ,magnetize a spot on the wire. As the wireadvances and this spot passes the pick-up head, an electrical pulse is generated by this head. .As a-..resu1t, the-repeater energizes h i ounter and applies an electrical pulse to the recorder'head, thereby magnetizing another .spot on the .wire. This spot isxinturn advanced to the; p ck-up head, and successive cycles 'of' operation continueas long as the wire is advanced. {Ijhus a pulsewi'll.begeneratedeach time the wire ration or .wave form of aeoaess advances a distance equal to the known distance between the recorder head and the pick-up head. The counter, which indicates the number of pulses generated by the pick-up head, therefore indicates the number of known lengths of wire passing the device, or may be calibrated to indicate directly the length of wire passing the device.

Reference is made to Fig. l. The invention is illustrated as it might be used in connection with reeling a continuous wire l onto a driven spool or reel l l. The wire HI may be assumed to be of ferromagnetic material, such as a plain carbonsteel. There is provided a recorder head 12 positioned adjacent the wire at a station A in the path of travel of the wire. The recorder head, which will later be described in more detail, comprises an electromagnet adapted to produce, when energized, a magnetic field in a small region in the path of the wire ID, of sufficient strength to magnctize an elementary length of the wire.

In the present illustration it may be assumed that the recorder head I2 is oriented so that it magnetizes the wire l0 chiefly longitudinally. It is'possi-ble, however, to modify the device so that the magnetic flux of the recorder head passes transversely through the wire, and in this case the wire would ofcourse become magnetized transversely. The magnetic field produced by the recorder head will vary with time in a manner dependent upon the current applied to the head. If this current is a series of separate pulses, and if the wire is advanced continuously, then the wire Will be magnetized in a series of spaced elementaryregions.

The recorder head [2 may be carried by a frame, not shown in Fig. 1, and there is provided a pick-up head l4, also carried by this frame, locatedat a station B in the path of travel of the wire [0, separated from the recorder head by a predetermined, known distance d. The pick-up head [4 which will be-described in more detail at a later point, is somewhat similar to the recorder head except that it is adapted to perform the reverse function, that is, to produce an electrical pulse when a magnetized portion of the wire I ll passes by the station B.

. Connected to the pick-up head M by a lead [5 there is provided electrical circuit means which may comprise a controlled pulse generator It. This pulse generator is responsive to electrical pulses derived from the pick-up head [4 and in a preferred form of the invention, provides an amplified output pulse for'each pulse derived from the pick-up head [4. The output pulses from the pulse generator I6 are applied, through a lead E1, to the recorder head l2. Thus when a magnetized portion of the wire Ill passes the pick-up head I 4, an electrical pulse is applied by this head to the repeater l6, which in turn applies an electrical pulse to the recorder head, thus magnetizing another spot on the wire. In one embodiment of the invention, the output pulse from the repeater l6 i'sof constant duration and wave form, regardless of the duthe pulse applied to this repeater. L

There is provided a counter [8, which may be connected to the output terminal of the repeater l6, adapted to Provide an indication proportional tothe number of pulses derived from the pickup head. In a modified embodiment, the counter. could be provided with a separate pick-up head, together with suitable amplifying means.

The apparatus is provided with initiator means l9, adapted to cause the recorder head l2 to be energized once initially when the measuring operation is begun. This initiator may comprise means for triggering the controlled pulse generator I6 once, as will :be illustrated subsequently in more detail. The initiator may conveniently be arranged as a portion of means for starting a motor, not shown in Fig. 1, which drives the reel II.

In summary, operation of the embodiment illustrated in Fig. 1 may be described as follows:

The initiator I9 is first actuated, causing an electrical pulse to be applied by the controlled pulse generator or repeater [6 to the recorder head 12, thereby magnetizing a first spot on the wire H). The counter 18 may have been previously adjusted so that this first pulse brings the counter up to the zero reading. The reel II is started, and the Wire I0 is caused to advance to the left in Fig. 1, as it is wound up on the reel. When the first magnetized portion; of the wire passes the pick-up head I4, an electrical pulse is applied by this head to the repeater or controlled pulse generator I6, which in turn applies a pulse to the recorder head [2 and a pulse to counter 18. If the length of wire passingthe apparatus is denoted by the symbol l, and the number of counts recorded by the counter I8, by the symbol n, then the following relation is observed to hold:

Z=nd

where d is the'known distance separating the recorder head at station A from the pick-up head at station B, as previously indicated. By proper calibration, the counter may be caused to' indicate length directly.

Reference is made to Fig. 2, which represents an embodiment of the device described in connection with Fig. 1, featuring 'a controlled pulse generator comprising a gaseous discharge tube, normally biased off, together with means for causing a temporary discharge through the tube. In Fig. 2 there is shown a recorder head 20, and a pick-up head 2!, supported adjacent the path of the wire ID and separated from each other a predetermined distance by a frame 22. These heads are generally in the nature of electromagnets, comprising a yoke of magnetic material, on which is wound a coil comprising a current path. Each yoke is provided with an air gap in a region adjacent the wire it. Performance is somewhat better if the air gap for the recorder head 20 is longer than the air gap for the pick-up head 2|. When the recorder head 20 is energized by current flowing through its coil, magnetic flux is induced around the yoke, and at the air gap this magnetic flux has a tendency to spread into the adjacent region. v As a result, magnetic flux passes through the wire it] at the station A, causing same to become magnetized with some degree of permanence.

When this magnetized portionof'the wire H) passes the pick-up head 21, it causes magnetic flux to be set up around the yoke of this head. As a result, there is a change in the flux linking the coil wound on this yoke, and hence a; voltage is generated across this coil. It may conveniently be assumed that the electrical pulse thus generated is of quite short duration. More particularly, the length of the magnetized portion of the wire, the speed of the wire, and the length of the air gap in the pick-up head are so related that the electrical pulse derived is of short duration comparedto thetime constants tential.

estates or the A.-C. coupled circuits into which it is fed.

"'Thereis provided'a'gas-tube23 having an anode 2l, -ac'athode anda grid 26. The cathode 25 is connected to ground through a resistor 21, and a parallel 'capacitor'2'la. The grid 26 is-connected through a resistor 28to a source ofnegative bias potential at a terminal 29, sufficiently negative to prevent initiation of a discharge through the tube, in the absence of other potentials'applied'to the grid circuit.

There is provided a pulse counter 30 of the type actuated by a solenoid 3|. The plate cir-" cuitiof'the tube '23 includes, 'in'ser'ies circuit relation, the coil of the solenoid'3l, the coil of th recorder head 20, a large resistor 32, and a source of positive potential at a terminal "'34. The terminal of the resistor32'oppositethe terminal'34 is connected "through a large capacitor 35 toiground. This resistor and capacitor comprise a; circuit for extinguishing conduction through-the tube '23 following a pulse, as will be described.

As part of the initiator, 'there are provided connections for'temporarily applying 'a'positive potential'to the grid 26 of the tube 23, including a capacitor '36 having one plate grounded and theother plateconnected to an arm of a switch 31. One'contactof the switch 31 is connected to name of positive potential at a terminal 38, and the-other contact is connected to the grid 26. The switch armis normally held, as by spring means not shown, in the down position, to cause the capacitor '36 to become charged from the terminali38.

As previously indicated, the tube 23 is normally non-conducting. At the startof 'a measuringoperation, the operator temporarilythrows the arm of .the switch 31 into the up position, causing the capacitor 36 to discharge through c resistor 28, thereby temporarily driving the grid 26 towarda positive potential. The change inpotentialcf thefgrid 26 is sufficient to initiate conduction throughthe plate circuit of the recorder head 20 and the solenoid 3|. The recorder head 20 magnetizes a spot on the wire l0, and the solenoid 3| causesthe'counter30 to operate'once. At the beginning of the discharge through 'the tube 23, a considerable portionjof thetube current is drawn from thelcapacitor '35, which had previously'been' charged. This capacitor is rather quickly discharged, however, becauseofthe low tube impedance typical of gas tubes during discharge, and a considerable current is caused to flow through the large resistor 32. The flow of plate current through the large resistor 32 causes a drop in the e'fiective plate supply voltage, and at the same time, the flow of current through the resistor 21 causes arise in the.,potential of thecathode. The capacitorf2'la tends tomaintain thecathode at a positive po- The plate-to-cathode voltage consequentlydecreasesbelow that necessarylto maintain -conduction throughthe tube, vandthe discharge isextinguished. It may be seen that the duration of the discharge through the tube 23 is-dependent upon circuit constants suchasthe size-of the resistor 32 and the capacitor 35,' and Iis ;sfibstantially"independent of the duration of .a

positive voltage applied to the grid. Oneend.of the coil of the pick-up'head 2| is groundedrandthe other end thereof. is connected through" a lead"39 to the input terminal of an amplifier"illll. 'Y'The outputterminaloflthis ampliiier is connected} through .a' bloclcing' capacitor ll to'the grid 26 of the tube 23. The windings of the coils ofthe recorder i'ind-pic'lr-up heads. and the --"stages of amplification between the pick-up head and the :grid 26 are so arranged series combination represented by windings o'f the counter 30 and the recorder head 20, adapted to provide an oscillatory parallel circuit, tuned to approximately the pulse repetition rate. This arrangement-has the effect of assuring that the anode 24 of the tube 23- will be driven sufii'cientl negative to extinguish the tube. I Reference is now "made to Fig. 3. In'this figu'rethere are "shown-a recorder head 50 and a pick-up head 51. As shown, the yokes-of these heads may be laminated, in order to reduce'eddy currents, "and improve the eificiency of the devices. Between the pick-up head 5| andthe recorder head 50 there is provided circuit means whichmay be considered to comprise a'pulserepeater circuit. There isalso provided a counter 52responsive to this circuit, and an initiator 53 for energizing sameat .the start of operations.

.One end of the coil of the pick-up head -5| mayhejgrounded, and'the other "end of this coil is .connected to theiirst of a series of "amplifiers 54,55 "and '56. These amplifiers serve "the purform amplitude. The polarity of the voltage pulse, in this illustrative embodiment, is shown at various pointsof the circuit'inFig. 3Q

There is provided a ,tube'5'l having its'grid normally .biase'd below/cutoff, being connected through a resi'stor'58 to a source of negative bias potential at the terminal 59. The windings of the recorder. and pick-up heads, and the stages of amplification are so arranged that when a magnetizedespot of the wire H) passes the pickup-head 5| ,anegative voltage pulse is applied to theinput terminal of the amplifier 54, and a positive-voltage pulseappears at the output terminalof the amplifier 56. This output'terminal is connected through a blocking capacitor!!!) to the gridof the tube 51. The cathode of the tube 5'! may be connected through a resistor 6!, in parallel with capacitor 62, to ground. The plate oflthis tubeis connected through a resistor 63 to a pos'itive'lpotential source or B'supply at'a terminal 64. Since the tube is normally biased off, the plate will'normally be at the positive 710a, ""llafand 12a, forward contacts 101), Ht,

and"| 2b, movable contact arms 100,1 I'c,'-and 12c, and. control coils :orwindings "10d, "lid, ;*and' 12d, respectively. The relays are an provided with spring not shown, adapted to urge. their mov able contact arms into therear position, that is,

toward the contacts 10a, I la, and-12a. I

The plate of the tube 51 is connected through a blocking capacitorI3 to oneend of the winding 10d, the other end of which is grounded. The rear contact m of the relay I is open-circuited, and the front contact I0b is grounded, 3 u The contact arm I00 is connected in series air-,- cuit relation with aresistor'III, the winding Nd, and a source of potential at a terminal I5, inthe order named. b v I The'rear contact 'IIa of the relay II is connected to one end 4 of the winding, I6 of the counter 52, theother end of this winding being connectedto a source ofdpotential at aterminalII. 1'

The movable arrnI Ic of the-relay II is grounded, The forward contact IIU-ofthe relay II is connected at a point I8 to one terminal of the initiator switch 53, the other terminal of this switch being grounded. Thepoint'IB is connected in serieswith a resistor IS, the winding 12d of. the relay I2, and a source of potential at a terminalfflc, in the order named The rear contact 12aof the relay I2 is connected to a source. of positive potential at a terminal 85. This potential may, for example, be of the order of 100 volts.

There is provided a capacitor 86, which may conveniently be of the order of 0.002 microfarad, for example, having one plate connected to the movable arm I2cand its other plate grounded. The forward contact 121) is con-" nected to a grid 81 of a multivibrator circuit, to be described, and is connected through a resistor 88 to ground. This resistor may conveniently be approximately 500,000 ohms. When the arm I20 is in therear position, the capacitor 86 becomes charged from the positive potentialso'urce at the terminal 85, and when the arm 120 is switched to the forward position, the capacitor 85 applies a temporary positive potential to the grid SI, and discharges "through the resistor 88.

There is provided, a multivibrator circuit of the single shotitype, including a pair of tubes 89 and 90. This multivibrator is; per se, conventional, irfconstructio'n, but will be described in detail for thesake of completeness. The'tube- '89 is provided with'a plate S5, a'cathode 96"and Y the grid BI, previously mentioned; The tube 90 is provided with a plate 91, a cathode 93'and 'a grid 99. The cathodes 96 and 9.8 are connected together, and are'conne'cted through a common cathode resistor I09 to ground. The plate 95, the plate 91, and the grid 99 are connected to a positive B supply terminal IOI through resistors I02, I03 and I04, respectively. The plate 95 is coupledto the grid 99 through a capacitor I05.

When the multivibrator is in its quiescent condition, the tube 90 conducts strongly, since its grid is held at a'positive potential because of being connected through resistor I04 to" the terminal IOI. vThe potential at p1ate.,9I is therefore considerably below the B supply potential. The tube 80, on the other hand,'normal1y issubstantially cut off,since the grid 8! is substantially at ground potential, and the cathode 96 is held at a considerable positive potential beca'use'of the conductionthrough the resistor I00'due to the plate current of the tube 90. When a positive pulse is applied to the grid 81, the tube 89 starts to conduct, and the plate 95 consequently drops in potential, forcing the grid 99 down in potential, and cutting ofi the tube 90. As a result, the potential of the plate 9! rises sharply.

ply potential because of the voltage drop through the resistor I02, and its right-hand plate "rising gradually toward the B supply potential. The grid 99, which is connected to the right-hand terminal of the capacitor I05, is thus gradually raised in potential, until it again causes thetube 90 to conduct. The increased cathode current raises the potential of the cathode 96, cuttin off the tube 89, and returning the multivibrator to its original quiescent condition. The plate 91 drops again in potential when the tube-90 again conducts, forming thetrailing edge of the output pulse from the multivibrator. It may be observed that the duration of the pulse generated by the multivibrator is determined by the circuit constants-of the multivibrator, and not by the wave form of the pulse applied to the grid '81..

The plate 91 'or the multivibrator circuit is connected through a blocking capacitor I06 to an amplifier I01 and thence through a blocking capacitor I08 to a grid I09 of a power amplifier tube. I I0. This tube is provided with a plate III and, with a cathode II2 connected to ground through a resistor I I3 and a parallel by-pass condenser I I I. The grid I09 is connected to ground through a resistor I5. The plate circuit of the tube I I0 is supplied with current from a B'supply terminal 'I I6 by a shunt feed, comprising an inductor III, connected between the terminal H6 and the plate III. The plate III is connected through a blocking capacitor IIB to one end of the winding of the recorder head 50, the other end of which is grounded.

The relays I0, II, and I2 are all so arranged that when a current flows through their respective windings, their movable arms are urged toward their contacts Illa, Na, and 12a. On the other hand, as previously indicated, when no current flows through. their windings, these arms' are urged by spring means toward the forward contacts 700, Nb, and 12b. When the apparatus is in a quiescent condition, no current is supplied to ,the winding 10d of the relay I0, and hence its movable arm is in the forward position. This completes a current path from the potential source at the terminal I5, through the winding IId, the resistor I4, the'switch arm I00, the contact 10b, to ground, and hence the winding IId is energized, thereby holding the switch arm He in the rear position, so as to engage the contact. IIa; Under this condition a steady direct current flows through winding I6 of the counter 52. The. winding 72d of the relay I2 is normally open-circuited, and hence the movable arm'lzc is normally in the forward position, engaging the contact 121). v r

The operation of the embodimentshown in Fig. 3 may now be summarized. At the start of operations, the initiator switch 53 is temporarily closed by the operator. A current path is thus temporarily established from the potential source at the terminal through the winding 72d, the resistor I9, and the switch 53, to ground. thus temporarily energizing the winding 72d and throwing the switch arm I20 into the rear position, engaging the'contact 12a. The capacitor 86 becomes charged almost instantaneously to the positive potential of the terminal 85, and when the. switch 53 is opened by the operator, de-ener'gizing the winding 72d, the capacitor is connected by the switch arm 72a to the contact 121 This contact may be considered to -comprise an output 86'; The capacitor 86, as it discharges through terminal for the capacitor the: resistor 88', thus applies'to the grid 81 of the: multivibrator circuit a positivepulse which serves to trigger the multivibrator, causing it in turn to deliver a positivepulse of fixed duration to theamplifier I01- and thence-to the power am- The poweramplifier in turn causes the recorder head '50 to magnetize a spot on. the wire. I

When the spot on the wire In magnet d by therecorder head 50 passes the pick-up head a: negative voltage pulse is applied by this pickup head to the input terminal of the amplifier rent path through the winding 'Hd of the relay II, de energizing this relay. As a result, the

spring; of thisrelay urges its contact arm intothe forward position to engage the contact 'IIb'.

-This motion of the contact arm 'llo has two ,effects, It opens the circuit through the wind inglBof the counter 52, and it completes a circuit through the winding 12d of the relay I2.

Upon termination of the pulse from the pickup head 5I, the movable arms of the relays are returned to their positions as shown in Fig. 3.

One feature of the system of Fig. 3 is that when the initiator switch 53 is closed, the recorder head is actuated, but the counter is not actuated. This feature simplifies the problem of initially setting the'counter. Thus the counter may be initially set at zero, and it will be first energized when, the wire has advanced by a distance corresponding to the separation of the heads. One complete operation of the counter takes place when the winding of its solenoid is ole-energized, and then againenergized.

In- Fig. 3, the leading edge of the pulse throws themovable arm lIc to the right or forward position, de-energ-izing the winding I5 of the counter 52, and causing the counter to perform a reaching stroke, and the trailing edgeof the,

pulse energizes the winding 16, causing the counter to perform a driving stroke, so as-to advance the length-indicating means ofthe counter.

This stroke of the counter 52 in Fig. 3 is slightly difierent from that of the counter 30 in Fig. 2.

The winding 31 of the counter 30 in Fig. 2 is normally de-energized. It is energized when the tube 23 fires upon the occurrence of the leading edge of the pulse, and is de-energized when. the

i tube 2-3. is extinguished, thereby performing one complete operationvor count.

Reference is; made. to Fig. l, wherein there is shown; in;,a-n illustrative embodiment a system employing the teachings of the present invention in wire reeling apparatus featuring means. for indicating and controlling thespeed at which the wire is being reeled, as well as for indicating and controlling the length of wire reeled. 1

In this system there is provided a reel I20 on which the wire ID is being wound, and a motor I2I' adapted to drive the reel I20 through a shaft or other mechanical linkage schematically indicated at I22. A recorder head I23, and a. pick-up head I24, separated from one another bya predetermined distance, are located adjacent the wire III. There is provided a repeater suchflas a pulse repeater circuit I25, responsive to the pickup head and adapted to actuate therecorder head, and an initiator switch I25 for initially actuating the pulse repeater circuit. The pulse repeater circuit is of the type adapted to provide anoutput. pulse thewave form of which is independent. of the wave form or duration of the pulse applied to'the input of said circuit... Thus if a series of ,pulses is, applied to the repeater I25, the output pulses from the repea'ter I25jwill all be similar to one another in amplitudajwave form and duration. The illustrative puls'elr'epeater circuitsv shown in Figs. 2 and 3 havethese characteristics, and may sometimes be. referred to as single-shotpulsing circuits, or single-shot pulse generators, becausethey produce vasingle output pulse for each input pulse appliedto them.

Connected to the output terminal of the pulse repeater I25 is aipulse counter I21, adapted to indicate the length".of the wire advancing past said heads, in a manner similar to the action of the counters of Figs. 1-3, inclusive.

Also connected to the output terminal. of the i pulse repeater circuit I25, and responsive to the pulses therefrom, is means for deriving a voltage determined by the repetition rate of said pulses.

, Such means may include a cathode follower.l.'28

and apdetector I30. The detector I30 inthe illustration comprises a rectifier I3I in series with a parallel circuit. comprisinga capacitor I.32..and a resistor I33. The cathode follower provides a low output impedance and a high input impedance so thatthe detector and circuits associated therewithwill not unduly load the pulse repeater circuit. The detector I30 is of the averaging type. That is, it provides an output voltage proportional to the average value of a periodic input voltage to this detector. The. input voltage to the detector in the present illustration comprises a series of. like positive pulses having a repetition rate determined by the velocity. of thewire Ill. The, shape of, the. pulses is. independent of. the wire velocity. During occurrence of a pulse,,the condenser. I32 charges, and. during the portion of thejcycle between pulses, this condenser partly discharges through resistor I33. If the wire moves rapidly, pulses will be applied to thedetector infquick succession, and the portion: of

cycle when theconden'ser I32 .is allowed tov discharge will be somewhat less than is the. case when the wire is moving, slowly. The output voltage fromv thedetector I35 will thuscompr ise a D.-C., voltage, determined by the repetition rate, of the pulses,'and, therefore determinedby the velocity ofjthe wire In.

(In a difierent .embodiment, itwould be possible to. employ, instead of a detector I30 of the averaging type, any other device adapted to-produce a voltage determined by the repetition rate of the pulses from thepulse repeater circuit.

Connected to the output. terminal I34 of the detector is an indicator device I35, such as a 11-0,. voltmeter, calibrated to read the velocity ergizing current of the motor I-2I. The speed controller I45 may in turn comprise'a voltage comparison circuit M-I, having a first input teracoaeee minal I42, a second input terminal I43 and an output-terminal I44. This comparison jcircuit,

. which may be of a known type, is adapted to produce at the terminal I44 a D.-C. voltage proportional to or determined by the difference between the voltages applied at the input terminals I42 and I43. The voltage at the output terminal I 44 may be known as an error voltage- Applied to the terminal I42 is a voltage adapted'to control the reeling speed to which the system adjusts itself. ,For this purpose, there is provided a potentiometer I45 one endof which is grounded and the other end of which is supplied with a positive D.C. potential at a terminal I46. The sliderrof the potentiometer is connected to the terminal I42. A manual control I41 is adapted to adjust the position of the slider, thereby controlling the voltage applied to the terminal I42, for adjusting the speed of reeling.

The terminal I34 is connected with theterminal I43, and there appearsat the terminal I44 a D.-C. voltage determined by the difierence between the actual velocity of the wire, as indicated by the'voltage at the terminal I34, and the desired velocity of the wire, as indicated by the voltage at the terminal I42. As part of the voltage-sensitive speed controller I40, and connected to the terminal I44, there is provided a motor control device I48, adapted normally to supply energizing current to the motor I2I through a pair of leads I49 and I50 and adapted to alter this energizing current in accordance with any error signal from the terminal I44. The control device is itself supplied with energizing current at a pair of terminals I I A switch I52 is shown in the lead I50, schematically illustrating. means for starting the motor. Of course in actual operation the starting mechanism would be considerably more refined.

Means are provided for automatically stopping the reeling operation after a predetermined length of wire has been reeled. For this purpose there is shown switch means adapted to open a circuit in the lead I50, a relay for controlling this switch means, and means responsive to the counter I21 adapted to control the relay. Comprising the switch means, there is provided a pair of contacts I53 and a movable contactor I54 engaging same, having an armature attached thereto. There is provided a solenoid winding I55, adapted to move the armatureupwardly when energized, thereby picking up the contactor I54 and opening the circuit in the lead I50, thus stopping the motor I2I. The current supply to the winding I55 is in turn controlled by a length control device I56. This device includes switch means in series circuit relationwith a source of a positive potential at a terminal I51, the winding I55, and a ground connection for this winding, and also includes a rotatable shaft I59 for controlling said switch means to complete the current supply circuit of the winding I55 when the shaft I59 has rotated through apredetermined distance. The shaft I59 is driven, with intermittent rotation, by the counter I21, and in factit may be considered to comprise an extension of the shaft of the counter which carries the rotary indicating device of the counter. It may thus be seen that when a predetermined length of wire has been reeled, the counter I21 will have rotated the shaft I59 through a corresponding distance, thereby causing the length control device I 56 to close the current supply circuit to the winding I55, which winding in turn lifts the contactor I54, and opens the current supply circuit to the motor I 2| so as to stop the reel; The length control device I56 is provided with a manually adjustable control l58 adapted toadjust the switch means in the device so as to determine the distance through which the rotary shaft I59 must turn in order to energize the winding I55. Hence the control I58 is adapted to determine the length of wire to be reeled before the motor is automatically stopped.

The operation of the device shown in Fig. 4 may be summarized as follows. The manual speed control I41 is initially adjusted to a setting corresponding to the speed desired for the reeling operation. The control I58 is adjusted to a setting corresponding to the length of wire desired to be reeled. The initiator I26 is operated to cause the recorder head to magnetize a first spot on the wire. The starting switch I52 is then closed to cause the reeling operation to start. While the wire velocity is below the desired speed, the'D.-C. voltage available at the terminal I34 will be smaller than that available at the terminal I42, and therefore an error signal will appear at the terminal I44 adapted to cause the motor control I48 to cause the motor to accelerate.

When the reeling operation is proceeding at the desired speed, the voltage at the terminal I34 will be equal to that at the terminal I42, and the potential at the terminal I44. applied to the motor control I48, will be that corresponding to zero error. Under this condition the motor control is adapted to energize the motor soas to maintain constant velocity.

If the reeling operation should proceed at 'too rapid a rate, the potential at the terminal I34 and consequently at the input terminal I43 of the comparison circuit 'I4I would become positive With respect to the potential at the input terminal I42 of the circuit, and as a resultfthere would appear at the terminal I44 a D.-C. voltage corresponding to an excess speed condition.

This potential would be applied to the motor control I48 which would in turn decrease the speed of the motor. 7 v

In general the error signals at the terminal I 44 corresponding to excess speed or less-than-desired speed will be positive or negative with respect to a reference potential, but of course this reference potential need not necessarily be ground or zero potential.

When the desired length of wire has passed the device, the counter I21 will have rotated the shaft I59 through a suflicient angle to cause the length control means I56 to energize the winding I55. As a result, the contactor I54 is lifted from the contacts I53, thereby de-energizing the motor, and stopping the reeling operation, as desired.

It is thus seen that the apparatus of Fig. 4 is capable of maintaining the linear velocity of the wire constant, as well as indicating this velocity, indicating the length of wire reeled by the apparatus, and stopping the reeling operation after the desired length of wire has been reeled.

After ferromagnetic wire has been passed through apparatus of the illustrative types described heretofore, the magnetized portions of the wire will tend to remain in a magnetized condition. If desired, these portions may be demagnetized by known methods, such as by subit maybe of considerable advantage at: a later time to be able to measure accurately a. length of this wire. Such a measuring operation. may

f ying circuit and a counter. For example, the apparatus of Fig. 2 might be employed for this subsequent operation, without the recorder head or the initiator. In this case the windi'n'gfof-the recorder 2!! would be replaced by an ordinary lead or electrical connection from the resistor 32 to the winding 3! of the counter. Of course in order tov calibrate the counter for this subsequent measuring operation, it would be necessary to take into account the distance separating the recorder and pick-up heads employed when the wire is first magnetized.

Throughout the present description it may be assumed that the wire or other material being measured is not stretched between the time it passes the recorder head and the time it passes the pick-up head.

In case a second pick-up head is employed to detect the magnetized spots at a later time, the length of the Wire should not be altered between the time it is magnetized and the time these magnetized portions are detected by this second pick-up head.

While it is preferable to magnetize the wire in short elementary lengths in order that the power requirements of the recorder head may be small and more especially in order that the electrical signal derived by the pick-up head may be in the form of short pulses which lend themselves to amplification by A.-C. coupled amplifiers, the present invention is not necessarily limited to this mode of operation. Thus for example the wire might be magnetized by energizing the recorder head with a square-wave current, symmetrical about the zero axis. In other words, the entire length of the wire might be magnetized in such a way that alternate segments or" equal length are magnetized with opposite magnetic polarity. The magnetic flux through the pick-up head would then have a square-wave variation, and a signal could be derived by the pick-up head adapted to control means for energizing the re corder head. The derived signal might be a square wave, or in case the time constants of the 7 various circuits were short compared with the period of the signal energizing the recorder head, the signal derived from the pick-up head might comprise alternate positive and negative pulses corresponding to the moments when the polarity ofthe magnetic flux through this head changed. These alternate positive and negative pulses could be use-cl to control means ior energizing the re corder head.

I It is also possible that the magnetizing currents of still difierent wave forms might be applied to the recorder head.

While the present invention has been described in its preferred form using electromagnetic recorder and'pick-up heads, other modifications are possible. Thus the recorder head may comprise a device adapted to heat a spot on any elongated advancing material by radiant heat or otherwise. A pick-up head may then be used adapted to detect the hot spot on the wire as it passes. For example, such a pick-up head may comprise a thermocouple. The pick-up head generates an electrical signal which is amplified and applied to a repeater circuit, thereafter being ap- 1.4 plied to therecorder head to heat a succeeding spot on the wire. In such an embodiment the recorder head may comprise an electrically-op erated radiant heater. In a system of this type, the pick-up and recorder heads should be located rather close to one another, and the wire should travel rather rapidly, since. the hot spdt. on the wire must be detectedbeioreit' has co'eled' too Thus in more general terms, the recorder head may comprise means for creating a localized condition of molecular disturbance in spaced portions of the material being advanced, and the pick-up head may comprise means located at a subsequent point in the path of the material for detecting said condition and for deriving a cyclic signal in response to passage of said portions. These signals are repeated and employed to control the recorder head. By counting the cycles of the signals, the length of the material may be determined.

It will be noted that the apparatus of the present invention is capable of measuring rapidly advancing wire or other material without touching it. That is, the recorder head and pick-up head are preferably spaced from the wire, and they act on it from a distance. This feature is of some advantage in that the heads do not impede the rapid advance of the material. Ihe invention would, however, operate satisfactorily even if the material comes into contact with the heads.

It may be further noted that the apparatus will measure the length of advancing material, regardless of whether the material advances continuously or intermittently.

While a suitable formof apparatus and method to be used in accordance with the invention have been described in some detail, and certain modifications have been suggested, it will be under stood that numerous changes may be made without departing from the general principles and scope of the invention.

I claim:

Apparatus for producing a series of current pulses, comprising a single-shot, self-restoring multivibrator having an input terminal and an output circuit, a magnetic recorder head connected to said output circuit, a continuously-advancing filament of ferromagnetic material moving past said recorder head, said recorder head being adapted, when energized by said multivibrator, to magnetize elementary portions of said filament, a magnetic pick-up head located in the path of said advancing filament subsequent to the position of said recorder head, a capacitor, a source of charging potential, relay means responsive to said pick-up head adapted to switch said capacitor first to said source of charging potential and then to said input terminal of said multivibrator for firing said multivibrator, and a resis- (References on following page) 15 REFERENCES CITED Number The following references are of record in the 2332797 file of this patent: UNITED STATES PATENTS Number Name Date 2,416,158 1,721,375 De Koning July 16, 1929 2,439,446 2,259,904 McNamee et a1 Oct. 21, 1941 2,466,251 2,277,579 Burger et a1. Mar. 24, 1942 2,493,028

Wilbur Aug. 3, 1943 10 2,559,849

16 Name Date Hume Oct. 26, 1943 Bindschedler et a1. June 20, 1944 Miller et a1. Dec. 11, 1945 Walstrom May 28, 1946 Coykendall Feb. 18, 1947 Begun Apr. 13, 1948 Martin Apr. 5, 1949 Putt Jan. 3, 1950 Covert July 10, 1951 

